Experimental and Spy Planes: Lockheed SR-71 Blackbird
by David Noland
The plane that literally grew several inches at Mach 3
When first revealed by President Lyndon Johnson in 1964, Lockheed's SR-71 spy plane stunned the world. Here was a plane that could cruise at Mach 3.3 (2,180 mph) and 85,000 feet, realms previously touched only briefly by experimental rocket planes. Aviation dreamers' most futuristic fantasies came true overnight.
The SR-71 had been designed and built in secrecy at the "Skunk Works," the clandestine Lockheed plant in Palmdale, Calif., headed by the legendary Clarence L. "Kelly" Johnson. Test flights were carried out at Area 51, the then-unknown "black" air base north of Las Vegas. The Blackbird's air of mystery, extraordinary performance, and sinister otherworldly appearance made it perhaps the most awe-inspiring aircraft of all time.
Development of the Blackbird started around the time Francis Gary Powers' U-2 spy plane was shot down over Russia in May, 1960. The first prototype, a single-seater called the A-11, made its first flight in 1962. A handful of improved A-12s flew CIA missions over Southeast Asia in 1967–68. A fighter spin-off called the YF-12A flew in 1963, but never reached production.
The SR-71, the larger two-crew Air Force version designed for strategic reconnaissance, first flew in 1964. Thirty-two were produced. From bases in Japan, England, and California, the SR-71 flew Cold War spy missions all over the world until 1990. None was ever shot down.
Retired in 1999
Blackbird fans wailed when the SR-71 was retired, but it had been rendered obsolete by spy satellites. (And perhaps by a rumored super secret next-generation Mach 6 spy plane called the Aurora.) After a brief reinstatement in 1995, the SR-71 fleet dwindled to three NASA research aircraft, which flew for the last time in 1999. Many SR-71s are now on display at museums around the country.
The Blackbird's extraordinary performance demanded extraordinary technology. Titanium alloy skin was necessary to resist the 600-degree temperatures caused by air friction at Mach 3. Skin panels had to have moveable joints to accommodate expansion and contraction with temperature changes. (The Blackbird literally grew several inches at Mach 3.) As a result, the SR-71 constantly leaked fuel on the ground. This necessitated a special heat-resistant non-volatile fuel called JP-7, used in no other aircraft.
Also unique were the moveable shock cones, or spikes, in the engine air intakes. At supersonic speeds, the spikes were positioned so that their shock waves fell within the inlet. This slowed and increased the pressure of the air as it entered the jet engine compressor. At Mach 3, the inlet pressure wave actually produced more thrust than the jet engine itself.
At 2,193 mph, the SR-71 still holds the official world speed record for air-breathing aircraft. No aircraft has ever taken off under its own power and flown faster. It's quite likely that none ever will.
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